Under-hyped is different from undervalued so I’m not sure that Greg Matthews’ answer quite addresses your question

with the large number of currencies in existence it’s difficult to keep up with what’s hot and what’s not but the best thing is to research and understand the activity level behind a currency and ask question. such as:

does the coin have an active development team?

what use cases does it serve?

how is the team marketing the coin?

what apps are being developed to use it?

is it listed on an exchange such that the public can purchase it easily?

the answers to such questions give you a perspective on whether there is potential behind the coin and allow you to compare hype against market valuations

a good example is a little-known coin called Einsteinium (EMC2). it was created a few years ago and all but died. in recent memory it has regained the market’s interest as developers and miners have begun lining up to get involved. the community is actively pursuing a number of interesting use cases and in my opinion there’s very little press about it, something that will change

currently pricing is hovering at around 3,000 satoshi/coin with a market cap of about $15M USD, but the coin could easily double or triple. only time will tell, of course, but given the Einsteinium Foundation’s agenda for growth and their active involvement with the energy sector, a super-wallet (in development) and various channels currently under exploration to provide a public on-ramp for the currency, it’s easy to see big gains coming in the mid-term

additionally, due to a technical issue where one of the exchanges (currently traded on Bittrex and Poloniex) discovered a double-spend (no one lost money but the issue had to do with under-capacity of hashpower on the network, which is being addressed as a high priority), the price at this point makes it a good buying opportunity